Which president was the most powerless and why?

I believe that the most powerless president was James Buchanan. He did absolutely nothing to stop the expansion of slave states, and didn't enforce the Compromise of 1850. The issue of slavery tied his hands for 4 years. Also, he was subject to rumors that he was a . That, too, made him more powerless. The whole issue and burden of slavery fell upon Abraham Lincoln, who followed Buchanan as president.